Vacuum vaporizing fixture



Apnl 14, 1964 R. P. RADKE ETAL VACUUM VAPORIZING FIXTURE Filed Dec 26, 1961 FIG.5

2| mill-m INVENTOR;

RICHARD P. RADKE BY-WILLIAM E.BI- A|R AGENT United States Patent 3,129,315 VACUUM VAPORIZING FIXTURE Richard P. Radke, Northridge, and William E. Blair, Redondo Beach, Calif., assignors to Lear Siegler, Inc., Santa Monica, Calif., a corporation of Delaware Filed Dec. 26, 1%1, Ser. No. 162,048 2 Claims. (Cl. 219-19) This invention relates to vacuum fixtures and more particularly to vacuum vaporizing fixtures used in a vacuum chamber in the vacuum deposition of thin films onto substrates.

The process of vacuum deposition is now used to produce microcircuitry, i.e., thin films of material conductive and non-conductive are vapor deposited on a substrate in given patterns through masks to form elements of the microcircuit.

A special fixture is used to evaporate the dielectric of a capacitor. This special fixture comprises a funnel-type tube being electrically connected to a power source at the top and bottom and surrounded by a housing. The funnel or tube has holes in it and the material, for example, silicon monoxide, is placed between the funnel and the housing. The funnel or tube is heated and the silicon monoxide vapor passes through the holes in the funnel up through the opening in the funnel and onto the substrate.

The disadvantage of the present system is that the silicon monoxide vapor has to pass through the holes in the funnel in order to go up through the funnel and onto the substrate. In practice, a small percentage of the vapor passes through the holes in the funnel and a large percentage of the vapor is lost by leaving the housing without passing through the holes in the funnel. The large percentage of the vapor which does not go through the funnel is not directed to the substrate, and, therefore, is effectively lost. Furthermore, since the efiiciency of the funnel is relatively low, a great amount of power is required to heat the funnel in order to get the desired amount of silicon monoxide vapor to pass through the funnel. The reason for using the funnel with the holes in it, is that vapor which passes to the substrate, must be all vapor and free of sputtered particles. Sputtered particles are caused when the silicon monoxide in the solid state is heated and the vapor effectively explodes small particles away from the main source. With the funnel, the small particles, first, have to pass through the holes in the funnel, and then usually hit the other Side of the funnel, which is extremely hot and which, thereby transforms the solid particles into a vapor state.

With the present known methods, the top of the housing around the funnel is left open and some of the particles of silicon monoxide leave the bulk of the material and hit the substrate thereby causing pin holes in the thin film deposited on the substrate.

It is, therefore, an object of this invention to provide a vacuum vaporizing fixture which does not allow particles to leave the fixture until they are in the vapor state.

Another object of the present invention is to provide a vacuum vaporizing fixture which is highly eflicient in directing the vapor from the fixture to the substrate.

Other objects and advantages of the present invention will become apparent from the following description when taken in conjunction witht he drawings, in which:

FIG. 1 is a schematic view of the present state of the art;

FIG. 2 is a cross-sectional drawing of the present invention;

FIG. 3 is a top view of the cover of the present invention;

FIG. 4 is a view taken along lines 44 in FIG. 3; and

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FIG. 5 is a cross-sectional view of a second embodiment of the present invention.

Referring to FIG. 1, a housing 10 encloses a filament 11. The filament is shown in schematic to show the principle of operation. Between the housing 10 and the filament 11 is a source of material 12, for example, silicon monoxide. The arrows 13 show the desired direction of the vapor, and the arrows 14 show the actual direction of a good portion of the vapr. In operation, the filament 11 is heated and the material 12 is vaporized and passes up through the filament 11. However, some of the material 12 leaves the housing 10 as small particles in the direction as indicated by the arrows 14.

Referring now to FIG. 2, the filament 15 has holes 16 therein. The filament 15 keeps the material between the housing 10 and the filament 15. A cover 17 rests on the housing 10 and accommodates the top of the filament 15 and also the electrical lead 18. The cover 17 may be made of any appropriate insulating material which can stand the high temperatures of the filament but is preferably made of ceramic material such as alumina. The housing 10 rests on an electrical insulator, not shown, so that no electrical insulation is required between the bottom of filament 15 and the housing 10. However, the bottom 31 of the housing 10 can be made of an insulating material such as ceramic, in which case the bottom 32 of the filament 15 is insulated from the walls of the housing 10.

The cover is shown in more detail in FIGS. 3 and 4. The hole 19 accommodates the filament 15 and a rectangular slot 20 accommodates the electrical lead 18. A flange 21 is provided on the periphery of the cover 17 so that a portion of cover 17 extends down into the housing 10. The cover 17 can be in two pieces with a diagonal cut 22. The cut 22 is made diagonal so that the vapor inside the housing will not escape through the space between the two halves of the cover 17. The cut may be tongue-and-grooved, or the like, so as not to allow a direct line between the inside of the housing 10 and the outside of the housing 10. The flange 21 is also made so that there is not a direct line between the inside of housing 10 and the outside of housing 10.

In operation, the filament is heated, as usual, but with the cover 17, any particles leaving the bulk of the material hits either the outside of the funnel, or if it passes through the hole, it hits the other side of the inside of the funnel, where it is evaporated due to the heat temperature of he funnel. Anoher possibilityis that the particle hits the cover 17. When the particle hits the cover 17, it either deposits there until a thick enough layer is built on the cover 17 to cause it to peel, chip, and fall down into the mass of material, or the cover 17-which is actually the case-is heated by the filament 15, and, therefore, the particle hits cover 17, vaporizes and passes through one of the holes in funnel 15 and out into the substrate. It has been found in practice, that the cover 17 actually gets hot enough to vaporize any particles hitting it. By this method, all of the vapor must leave the fixture through the top of the funnel 15 and thereby is directed to the substrate.

The second advantage of this invention is that only vapor leaves the fixture and the particles which cause pin holes in the thin film deposited either remain in the fixture until vaporized or are vaporized on the inside of the funnel 15.

FIG. 5 shows the second embodiment of the present invention wherein flange 23 is placed on the inside of housing 10, flange 24 is placed on the outside of the funnel 15, and flanges 25 and 26 are placed on either side of the electrical lead 18. The flanges can be, for example, made from tantalum or any similar material,

which will withstand the high temperatures of the filament.

The flanges 23, 24, 25, and 26 further insure that there is no direct line between the inside of the housing and the outside of the housing. Furthermore, they allow the cover 17 to be made with less precision, thereby reducing the cost of the cover 17.

The present invention has been used and it was found that for a given source, for example, silicon monoxide, at a given distance of twelve inches from the substrate on which the thin film is to be deposited, required only 500 watts of power as opposed to 1,200 watts of power in the previous fixtures. Also, it only took one and a half minutes to obtain the same film thickness which previously required four minutes. The present invention, therefore, provided a 60% reduction in power and a 60% reduction in time to produce a film of the same thickness under similar environmental parameters as produced by the present fixtures. It was also noted that the amount of material wasted in the present fixtures was 85% as opposed to 15% in the first embodiment of of the present invention and of wasted material in the second embodiment of the present invention.

This invention, therefore, provides a major improvement over the present state of the art of vacuum vaporizing fixtures.

Although this invention has been particularly described above, it is not intended that it should be limited by the above description, but only in accordance with the spirit and scope of the appended claims.

What we claim:

1. In combination:

a cylindrical filament having an opening at one end and a plurality of perforations distributed over the length of the walls thereof,

a cylindrical housing having an open end to accommodate said filament such that a space exists between the outside of said filament and the inside of said housing,

cover means comprising a heat resistant plate having a first opening therein to accommodate said perforated filament and a second opening to accommodate an electrical lead to said filament, and

wherein said filament is capable of being heated so that the material placed in the space between said housing and said filament is vaporized and such vapor is capable of passing through said perforations and out at open end of said filament.

2. The apparatus of claim 1 in which flange means .are located on the inside of said housing and on the outside of said filament so as to support said cover means.

References Cited in the file of this patent UNITED STATES PATENTS 1,613,777 Worn Jan. 11, 1927 1,712,403 Ruggles May 7, 1929 2,440,135 Alexander Apr. 20, 1948 2,664,852 Chadsey Jan. '5, 1954 2,762,722 Truby Sept. 11, 1956 2,772,318 Holland Nov. 27, 1956 2,885,997 Schwindt May 12, 1959 3,017,851 Krause Jan. 23, 1962 OTHER REFERENCES Germany, N6323VI/48b, May 3, 1956. 

1. IN COMBINATION: A CYLINDRICAL FILAMENT HAVING AN OPENING AT ONE END AND A PLURALITY OF PERFORATIONS DISTRIBUTED OVER THE LENGTH OF THE WALLS THEREOF, A CYLINDRICAL HOUSING HAVING AN OPEN END TO ACCOMMODATE SAID FILAMENT SUCH THAT A SPACE EXISTS BETWEEN THE OUTSIDE OF SAID FILAMENT AND THE INSIDE OF SAID HOUSING, COVER MEANS COMPRISING A HEAT RESISTANT PLATE HAVING A FIRST OPENING THEREIN TO ACCOMMODATE SAID PERFORATED FILAMENT AND A SECOND OPENING TO ACCOMMODATE AN ELECTRICAL LEAD TO SAID FILAMENT, AND WHEREIN SAID FILAMENT IS CAPABLE OF BEING HEATED SO THAT THE MATERIAL PLACED IN THE SPACE BETWEEN SAID HOUSING AND SAID FILAMENT IS VAPORIZED AND SUCH VAPOR IS CAPABLE OF PASSING THROUGH SAID PERFORATIONS AND OUT AT OPEN END OF SAID FILAMENT. 